Police said at least two people were attacked by criminal “flash mobs” in the Streeterville neighborhood on Saturday night.

The first attack happened around 8:25 p.m. Saturday when a man was attacked after parking his motor scooter near the Northwestern University campus in Streeterville.

The man had parked on the 300 block of East Chicago Avenue across the street from Wieboldt Hall when a group of 15 to 20 men, all approximately 16 to 20 years old and black, approached him, according to an alert from the university.

A few minutes after that attack, man riding his bicycle on the lakefront path at 701 N. Lake Shore Dr. was attacked by a group of teenagers, who punched and kicked him and stole his cell phone, sources told WBBM Newsradio 780.